The present invention generally relates to a defibrillation system including an atrial defibrillator for applying cardioverting electrical energy to the atria of a human heart in need of cardioversion. The present invention is more particularly directed to such a system having a portable communication device operable by a patient for selectably initiating atrial fibrillation detection without committing to atrial cardioverting therapy.
Atrial fibrillation is probably the most common cardiac arrhythmia. Although it is not usually a life-threatening arrhythmia, it is associated with strokes thought to be caused by blood clots forming in areas of stagnant blood flow as a result of prolonged atrial fibrillation. In addition, patients afflicted with atrial fibrillation generally experience palpitations of the heart, and may even experience dizziness or even loss of consciousness.
Atrial fibrillation occurs suddenly, and many times can only be corrected by a discharge of electrical energy to the heart. Implantable atrial defibrillators have become a reality to provide relief to patients suffering from occurrences of atrial fibrillation.
For example, implantable atrial defibrillators and lead systems which exhibit complete automatic operation are fully described in U.S. Pat. No. 5,282,837, issued Feb. 1, 1994, for xe2x80x9cImproved Atrial Defibrillator and Method,xe2x80x9d U.S. Pat. No. 5,350,404, issued Sep. 27, 1994, for xe2x80x9cLead System for Use with an Atrial Defibrillator and Method,xe2x80x9d and U.S. Pat. No. 5,207,219, issued May 4, 1993, for xe2x80x9cAtrial Defibrillator and Method for Providing Interval Timing Prior to Cardioversion,xe2x80x9d all of which patents are assigned to the assignee of the present invention and incorporated herein by reference. Each of these patents discloses and claims an implantable atrial defibrillator wherein atrial fibrillation is automatically detected and, when needed, cardioverting electrical energy is applied to the atria to terminate the atrial fibrillation episode and return the heart to normal sinus rhythm.
As with any implantable device, it would be desirable to be able to provide the patient with some manual control for the implanted device. For example, implantable pacemakers known in the art may be totally deactivated by placing a magnet over the implant site. The magnetic field of the magnet causes a reed switch within the implanted device to remain either open or closed as long as the magnet is held there. Other magnet modes are known for checking the power levels of the implanted device battery, for example.
While magnets have proven effective in the past, they are not convenient to use. First of all, such magnets are heavy and, in most uses, rather large, making them difficult to carry in a pocket or purse. Also, because the magnets produce a magnetic field, they can erase dictation or other type of audio tape to which they may come into close proximity within a purse or pocket. Under such conditions, they can also erase the magnetic strips on credit and bank cards. They would further erase floppy disks for computers.
Providing some manual control over an implanted atrial defibrillator is described in U.S. Pat. No. 5,490,862. There, a magnet is described for generating external commands which cause the defibrillator to enter an atrial fibrillation detection and committed therapy sequence. A magnet is certainly effective for such use. However, in addition to the drawbacks previously mentioned, magnets do not provide any means for feedback to inform the patient that the implanted device is acting upon the external command. An acknowledgment of receipt of a command and the fact that the implant is implementing the command would be important feedback to patients. This is especially true if the patient is attempting to have the implanted device initiate required therapy.
In answer to the problems resulting from the use of magnets in such systems, an atrial defibrillation system including an external communication device dimensioned to be hand-held is disclosed and claimed in U.S. Pat. No. 5,674,249 which issued on Oct. 7, 1997 for xe2x80x9cAtrial Defibrillation System Having A Portable Communication Device,xe2x80x9d and which is incorporated herein by reference. The portable communication device there disclosed includes an RF transmitter for transmitting a command signal to the implantable defibrillator. The implantable defibrillator includes a receiver for receiving the command signals and performs a task responsive to receipt of the command signal. An RF transmitter within the implantable device transmits an acknowledgment signal back to the portable communication device upon receipt of the command signal. The portable communication device further includes a receiver which receives the acknowledgment signal and provides a perceptible indication responsive to receipt of the acknowledgment signal to the patient. In this way, the patient knows that the command was received and that the implanted device is performing the desired task.
While the last two mentioned atrial defibrillation systems go a long way towards providing effective and positive control of an implantable atrial defibrillator by the patient, they do not provide a complete answer. For example, they provide for very limited operational modalities of an automatic mode, a patient activated mode, and a combination of these two modalities. In all of these modalities, the patient is committed to cardioverting therapy if atrial fibrillation is detected. In the automatic mode, atrial fibrillation detections most often occur when the patient is not in atrial fibrillation. Many atrial fibrillation patients are highly symptomatic when experiencing atrial fibrillation. Automatic detection for these patients can represent unwarranted depletion of the defibrillator power source. Further, a patient may not be in a position to receive cardioverting therapy at a time when the committed therapy is to be delivered. At other times, a patient may simply want to confirm the absence of atrial fibrillation or be able to determine that the atrial fibrillation detector of the patient""s defibrillator agrees with patient""s perception of the arrhythmia. Hence, there is a need in the art for an atrial defibrillation system which enables a patient to select and activate atrial fibrillation detection without committing to cardioverting therapy.
The invention provides an atrial defibrillation system including an implantable atrial defibrillator including an atrial fibrillation detector for detecting atrial fibrillation and a cardioverter for cardioverting the atria of a heart. The implantable atrial defibrillator further includes a receiver for receiving commands from an external nonimplanted transmitter. The system further includes a nonimplantable communication device including a transmitter for transmitting a command to the receiver for activating only the atrial fibrillation detector to cause the atrial fibrillation detector to detect for atrial fibrillation.
The present invention further provides an atrial defibrillation system including an implantable atrial defibrillator including an atrial fibrillation detector for detecting fibrillation of a patient""s atria, an atrial cardioverter for applying cardioverting electrical energy to the patient""s atria, a receiver for receiving operation commands transmitted from an external transmitter, and a mode selecting stage for causing the defibrillator to operate in a first mode of operation wherein only the atrial fibrillation detector is activated to detect for atrial fibrillation or in a second mode of operation wherein the atrial fibrillation detector is activated to detect for atrial fibrillation and then the cardioverter is activated for applying cardioverting electrical energy to the patient""s atria if atrial fibrillation is detected. The system further includes a nonimplantable communication device dimensioned to be hand-held and operable by the patient including a transmitter for selectively transmitting a first operation command to cause the mode selector stage to render the implantable atrial defibrillator in the first mode of operation and a second operation command to cause the mode selector stage to render the implantable atrial defibrillator in the second mode of operation.